Illustrated guide r22 effective walls in wood frame construction

ILLUSTRATED GUIDE R22+ Effective Walls in Wood-Frame Construction in British Columbia

This guide was developed to assist home designers and builders in the City of Vancouver build walls with R22 or greater thermal performance.

The information included in this guide is relevant for low-rise woodframe residential buildings across British Columbia.

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Preface About this Guide The Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia is published by BC Housing. This guide consolidates informa on on above and below grade wall assemblies for low-rise wood-frame buildings which are capable of mee ng R-22 or greater effec ve thermal performance. This level of thermal performance is required by the 2014 Vancouver Building By-law and by the 2012 BC Building Code for Climate Zones 7B and 8, and represents a significant increase in the required level of performance from previous codes. The guide is intended to be an industry, u lity, and government resource with respect to mee ng this thermal performance level, while not compromising other aspects of building enclosure performance, including moisture management, air leakage, and durability.

The informa on included in this guide applies to low-rise wood-frame detached and semi-detached (e.g. duplex to quadplex) homes, and row-houses/townhomes within Bri sh Columbia. Non wood-frame homes, manufactured homes, and mul -unit residen al buildings are beyond the scope of this guide. Addi onally, while this guide provides general guidance on assembly selec on and key considera ons, it does not provide informa on on detailing of the assemblies at transi ons and penetra ons.

It is important to note that each building and construc on project is different and presents unique challenges and considera ons. This guide presents an overview of poten ally applicable assemblies to meet higher thermal performance targets, but it is likely that these methods will need to be modified to accommodate varia ons in each project. It is recognized that alterna ve wall assemblies exist beyond the scope of this guide.

Disclaimer This guide is provided for general informa on only except where noted. The greatest care has been taken to confirm the accuracy of the informa on contained herein; however, the authors, funders, publisher, and other contributors assume no liability for any damage, injury, loss, or expense that may be incurred or suffered as a result of the use of this publica on, including products, building techniques, or prac ces. The views expressed herein do not necessarily represent those of any individual contributor, BC Housing, or the City of Vancouver.

Building science, products, and construc on prac ces change and improve over me, and it is advisable to regularly consult up-to-date technical publica ons on building envelope science, products, and prac ces rather than relying solely on this publica on. It is also advisable to seek specific informa on on the use of products, the requirements of good design and construc on prac ces and requirements of the applicable building codes before undertaking a construc on project. Consult the manufacturer’s instruc ons for construc on products, and also speak with and retain consultants with appropriate engineering or architectural qualifica ons, and appropriate municipal and other authori es, regarding issues of design and construc on prac ces. Most provisions of the building codes (Bri sh Columbia Building Code and the Vancouver Building By-law) have not been specifically referenced, and use of the guide does not guarantee compliance with code requirements, nor does the use of systems not covered by this guide preclude compliance.

Always review and comply with the specific requirements of the applicable building codes for each construc on project. The materials and colours shown as examples in the guide are not intended to represent any specific brands or products, and it is acknowledged that many product op ons exist.

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Acknowledgements This guide was funded and commissioned by the City of Vancouver and BC Housing, and was prepared by RDH Building Science Inc. Acknowledgement is extended to all those who par cipated in this project as part of the project team or as external reviewers.

Authors Primary Author: Primary Reviewer: Graphics:

Lorne RickeDs, MASc, EIT - RDH Building Science Inc. Graham Finch, Dipl.T., MASc, P.Eng - RDH Building Science Inc. James Higgins, Dipl.T. - RDH Building Science Inc.

External Reviewers Pierre Busque - Busque Engineering Ltd. Wei Chen - Exp Global Inc. Murray Frank - Construc ve Home Solu ons Inc. Maura Gatensby - Architectural Ins tute of Bri sh Columbia Stan Jang - Building Balance Consul ng Inc. Richard Kadulski - Richard Kadulski Architect Mark Lawton - Morrison HershďŹ eld Limited Zachary May - Building and Safety Standards Branch John Nicol - Building and Safety Standards Branch Monte Paulsen - Red Door Energy Design Ltd. Deborah van der Horst - H&H Small Space Solu ons Inc.

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Table of Contents Introduc on Building Enclosures Overview

2

R-value Calcula ons

3

Wall Thickness and R-value

4

Air Barrier Systems

5

Environmental Design

8

Cladding Support & Fasteners Through Exterior Insula on

9

Cladding Support Op ons

10

Structural Considera ons

11

Installa on Methods

15

Fastener Tables

16

Above Grade Walls

18

Split Insulated Walls

19

Exterior Insulated Walls

23

Double Stud Walls

25

Deep Stud Walls with Service Wall

27

Below Grade Walls

29

Exterior Insulated Walls

30

Interior Insulated Walls

32

Alterna ve R-22 Walls

34

Walls Less Than R-22

38

Summary

40

Summary of Walls Addi onal Resources

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Introduc on This sec on provides an introduc on to the guide including sec ons on the following: Building Enclosures Overview R-value Calcula ons Cladding ADachment Wall Thickness and R-value Air Barrier Systems Environmental Design & Ra ng Overview

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Building Enclosures Overview The building enclosure is a system of materials, components, and assemblies that physically separate the exterior and interior environments. It comprises various elements including roofs, above grade walls, windows, doors, skylights, below grade walls, and floors, which in combina on must control water, air, heat, water vapour, fire, smoke, and sound. Addi onally, the enclosure is an aesthe c element of the building.

To perform these func ons, building assemblies typically use a series of layers, each intended to serve one or mul ple func ons within the building enclosure. As an example, for an above grade wall, cladding is typically installed to provide the aesthe c exterior finish as well as the primary water shedding surface. A water resis ve barrier (WRB) is installed inboard of the cladding as a secondary barrier to moisture to prevent water ingress, and a drainage gap is installed between the cladding and WRB to allow drainage of water which penetrates past the cladding. This approach is commonly referred to as a rainscreen wall assembly. Insula on is installed to control the flow of heat (i.e. energy transfer) through the enclosure, and an air barrier is installed to control bulk air movement through the wall. A vapour barrier is also installed to control diffusion of water vapour through the wall assembly, and while typically a very impermeable material is used for this func on (i.e. Type 1 vapour barriers less than ≈6 ng/(s•m²•Pa)), more permeable materials can also fulfill this func on (i.e. Type 2 vapour barriers less than 60 ng/(s•m²•Pa) and smart vapour retarders). In many cases these func ons can be provided in combina on by a single layer within the assembly; for example, the WRB and air barrier may both be provided by the sheathing membrane. The rela ve posi on of these different elements of the enclosure assembly and appropriate detailing of the building enclosure systems at transi ons and penetra ons is fundamental to their performance.

This guide focuses on wall assemblies which can achieve an effec ve thermal performance of approximately R-22 (R-21.86, RSI-3.85) while s ll mee ng the other performance requirements for enclosure assemblies. These rela vely insula ve wall assemblies help to reduce the transmission of heat energy through the building enclosure and consequently reduce the hea ng and cooling loads of the building, and the overall building energy consump on.

Note on BC Building Code (BCBC) and Vancouver Building By-law (VBBL) Compliance In many cases this guide indicates best prac ces with respect to air, vapour, and moisture management, rather than minimum requirements as specified by relevant building regula ons. This approach is intended to promote the construc on of effec ve and durable assemblies. Furthermore, in some cases the guide iden fies materials, assemblies, or prac ces for which a registered professional (BC architect or engineer) may be required by the authority having jurisdic on to indicate equivalency for compliance with relevant building regula ons. Relevant building regula ons should be reviewed and complied with for each project.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

R-value Calcula ons The thermal resistance of building assemblies is commonly indicated using R-value provided in imperial units of “M²•°F•hr/Btu”, and can also be provided as RSI-values in metric units of “m²•K/W”. All R-values in this guide are provided in imperial units as the building industry is most familiar with these units. The higher the R-value, the beDer the thermal performance. U-values are another way of describing heat flow through a wall, and are the inverse of R-values. The lower the U-value, the beDer the thermal performance.

R = 1/U

RSI-1 m²·K/W = R-5.678 B²·°F·hr/Btu

Material proper es, air film proper es, framing factors (% of the wall area which is framing), and the treatment of thermal bridges for calcula ng R-values (RSI-values) are provided in appendix Sec on A9.36.2.4 of the BCBC. For all calcula ons in this guide, a 23% framing factor was used corresponding with standard framing prac ces for 16” spaced studs. Part 9 of the BCBC does not require accoun ng of thermal bridging by discon nuous cladding supports through the exterior insula on such as fasteners or brick es, or by other penetra ng elements such as pipes, ducts, shelf angles, anchors and es, and minor structural members that must par ally or completely penetrate the building enclosure to perform their intended func on. Major penetra ons such as balconies, beams, and columns do not need to be included as long as they form less than 2% of the gross wall area, and the surrounding insula on is installed ght against the penetra ng element.

Con nuous cladding supports such as strapping which penetrates the insula on should be accounted for. Thermal calcula on requirements are different for buildings covered by Part 3 of the BCBC.

Interior Air Film

+ +

R-13.4 (RSI-2.36)

(RSI-3.95)

R-0.68 R-0.45 (RSI-0.08) (RSI-0.12)

+

AI = 77% Insula on RI = R-19

AF = 23% Framing RF = R-6.8

100

100 AF A + I RF RI

= R-22.4

Fiberglass BaD Insula on (R-19)

R-0.17 R-0.10 R-1.02 R-6.0 R-0.61 (RSI-0.03) (RSI-0.02) (RSI-0.18) (RSI-1.06) (RSI-0.11)

1/2” Drywall

+

2x6 Stud Wall w/ R-19 Fiberglass BaDs

+

7/16” OSB Sheathing

+

1 1/2” Exterior Insula on (R-4/inch)

3/4” Ven lated Air Space (neglects furring)

+

2x6 Wood Studs

Split Insulated Wall

+

Cladding (3/4” Stucco on Backerboard)

=

Exterior Air Film

For low-rise wood-frame residen al construc on, R-values can be calculated according to Sec on 9.36 of the Bri sh Columbia Building Code (BCBC). (The City of Vancouver has not specifically adopted this sec on; however, it provides useful guidance for calcula ng compliance.) This sec on specifies that R-values will be calculated using the Isothermal Planes method. This method assumes that the boundary between each layer of a building assembly is at constant temperature, which is a rela vely appropriate assump on for wood frame construc on with rela vely low conduc vity structural members; however, with conduc ve structural members such as steel studs, this calcula on method should not be used. The R-value of layers of the wall assemblies which include mul ple components, such as insulated stud walls, should be calculated using the Parallel Paths method (i.e. area weighted U-value calcula on). An example wall R-value calcula on for an assembly and for the insulted stud layer of the assembly are shown below.

=

23 6.8

+

77 19

= R-13.4 Page 3

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Wall Thickness & R-value When construc ng rela vely more highly insulated wall assemblies, a common concern is the increase in wall thickness compared to conven onal (i.e. less insulated) assemblies. This increase in thickness can poten ally have an impact on requirements with respect to floor space limita ons and setback distances to property lines. To aid in selec ng the op mal wall arrangement for a given project, the chart below indicates the total thickness and effec ve R-value of a number of the different assemblies in this guide. The values provided in the chart correspond with the tabulated R-values provided in each relevant sec on of the guide, and consequently, addi onal informa on on each of these assemblies is provided in the associated sec on.

Wall Effec ve R-value versus Total Thickness

This chart indicates that, of the assemblies discussed in this guide, a split insulated 2x4 wall provides R-22 effec ve thermal resistance in the least total wall thickness. Despite this, different wall assemblies will oMen be selected to meet other design criteria including water and vapour control, constructability, familiarity, and aesthe cs.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Air Barrier Systems An air barrier system is used to control the flow of air into and out of a building. Control of these airflows is important to limit energy loss due to exfiltra on, to reduce the poten al for air leakage and associated condensa on, for occupant comfort, and for indoor air quality. In the City of Vancouver, new residen al construc on must achieve an air ghtness of 3.5 ACH501. No such requirement currently exists in the rest of Bri sh Columbia.

For an air barrier to be effec ve, it must meet five design requirements: All the elements (materials) of the air barrier system must be adequately air-impermeable.

The air barrier system must be con nuous throughout the building enclosure including at transi on and penetra on details.

The air barrier system must be structurally adequate or be supported to resist air pressure forces due to peak wind loads, sustained stack effect, and mechanical equipment such as fans.

The air barrier system must be sufficiently rigid or be supported so that displacement under pressure does not compromise its performance or that of other elements of the assembly.

The air barrier system should have a service life as long as that of the wall and roof assembly component or alternately be easily accessible for repair or replacement.

A number of different systems exist which can fulfill these requirements, and each has poten ally posi ve and nega ve aDributes.

Interior Air Barrier Systems Sealed Polyethylene (or Other Membranes) - In the sealed polyethylene sheet air barrier system approach, the polyethylene sheet installed to the interior of the stud cavity is sealed at all transi ons and penetra ons with tapes and sealants to provide a con nuous air barrier system. The polyethylene sheet is clamped between the framing and the gypsum wall board which provide the necessary structural support. A similar approach can also be used with alterna ve sheet products such as smart vapour retarders or other appropriate plas c membranes.

Air ght Drywall Approach (ADA) - In the ADA, the interior gypsum wall board (i.e. drywall) provides the air barrier system, and con nuity is maintained using sealants and/or gaskets.

Special aDen on must be paid to ensure con nuity at intersec ons of the exterior walls with par on walls, ceilings, and floors.

Exterior Air Barrier Systems Sealed Sheathing - The sealed sheathing air barrier system approach consists of sealing the joints between sheathing boards using membrane, tape, or sealant so that the sheathing itself provides the air barrier. As the sheathing itself is rigid and fastened to the studs, no addi onal support is typically required for this system.

Sheathing Membrane - The sheathing membrane, which is usually installed as a water resis ve barrier (WRB), can also be func on as the air barrier. Both mechanically fastened and selfadhered sheet membranes can poten ally be used. For mechanically fastened systems, the laps between sheets should be sealed, and in all systems penetra ons and transi ons should be sealed. While adhesion and fastening of these systems provides some support, oMen the wood strapping or exterior insula on provide improved support for these systems.

Spray Foam - Both open cell and closed cell spray polyurethane foams can be used as an air barrier, and are oMen used at penetra ons and transi ons to accommodate complex geometries; however, these products can also be used within the stud cavi es or on the exterior to provide the main component of the air barrier system. Joints, cracks, and gaps that are too small to be effec vely sealed with spray foam (such as between boDom plate and floor, or between double top plates) should be sealed with other sealants or adhesives.

1

ACH50 means air changes per hour measured at a 50 Pa pressure difference across the exterior building enclosure. It is also possible to meet this requirement in Vancouver by sealing according to good engineering prac ce with visual confirma on by a cer fied Energy Advisor.

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Air Barrier Systems

Interior Air Barrier Systems Typically the most important considera on in designing an air barrier system is maintaining con nuity at transi on and penetra on details. A selec on of these key details are provided below, which graphically indicate poten al methods for maintaining air barrier con nuity. Note that various other important details exist, and alternate methods for ensuring con nuity are possible. These details are for a polyethylene sheet air barrier, but other interior air barrier systems such as air ght drywall should also address con nuity at these key loca ons. Various other resources with respect to air barrier detailing are provided at the end of this guide.

Roof to Wall Transi ons

Above Grade to Below Grade Wall Transi ons

Compared to exterior air barrier systems, one advantage of interior air barriers is that typically the roof to wall transi on is more straighVorward. In the above detail, con nuity at the transi on is provided simply by taping the polyethylene sheet in the ceiling to the sheet in the wall.

Where the above grade walls meet the below grade walls it is important to ensure that the air barrier system maintains con nuity. In the above detail, blocks of air-impermeable insula on are cut and installed between the joists, and spray foam is used to seal around their perimeter.

Electrical Receptacles Penetra ons

Rim Joist Transi ons

Penetra ons through the air barrier should be sealed to ensure con nuity. In the above detail, an electrical receptacle is sealed using a pre-made polyethylene boot, which is then sealed to the polyethylene sheet air barrier. When using interior air barrier systems, penetra ons that require sealing are oMen numerous.

They may include pipes, light ďŹ xtures, fans, and structural members.

When using an interior air barrier system, oors of the building interrupt the air barrier and transi on detailing is required. In the above detail, blocks of air-impermeable insula on are cut and installed between the joists, and spray foam is used to seal around their perimeter. These loca ons should be insulated to the same level as the adjacent wall.

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Air Barrier Systems

Exterior Air Barrier Systems While placing the air barrier on the exterior will typically simplify and reduce the number of air barrier transi ons and penetra on that must be dealt with, a variety of key details s ll exist which should be carefully considered. A selec on of these key details are provided below which graphically indicate poten al methods for maintaining air barrier con nuity at these loca ons. Various other important details exist, and alternate methods for ensuring con nuity are possible. These details are for a mechanically fastened sheet sheathing membrane, but can be adapted for other systems such as adhered sheathing membranes.

Roof to Wall Transi ons When an exterior air barrier system is used, oMen one of the challenging transi on details is at the roof-towall interface. The adjacent detail indicates transi on of the air barrier from the sheathing membrane to the polyethylene sheet in the ceiling via adhered membrane, sheathing, sealant, top plate, and then sealant. Alterna ve methods for this detail include pre-stripping a sheet air barrier material between the plates prior to installa on of the roof truss.

Mechanical Ducts or Other Penetra ons Penetra ons through the air barrier should be sealed to ensure con nuity. In the adjacent detail a duct penetra on is sealed using a foil-faced transi on membrane and sealant. The hood is also sealed to the duct to prevent the exhaus ng of humid air into the wall cavity. Other penetra ons which should be sealed include pipes, wires, conduits, structural members, and decora ve accessories.

Above Grade to Below Grade Wall Transi ons Where the above grade walls meet the below grade walls it is important to ensure that the air barrier system maintains con nuity. In the adjacent detail a combina on of sheathing tape and an adhered membrane are used to transi on from the sheathing membrane to the below grade waterprooďŹ ng membrane.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Environmental Design While a wall R-value performance target of R-22 works to significantly reduce the energy consump on of the building as compared to buildings with less insulated walls, when selec ng wall assemblies, it is also important to consider the overall environmental impact.

This guide uses a three-leaf scale to indicate the rela ve complete life-cycle environmental impact of each of the wall assemblies. Each of the three leaves corresponds with a different part of the life-cycle of the wall assemblies: Materials and Construc on, Ease of Modifica on, and End of Service Life. The evalua on with respect to these three categories is then combined to create a total cumula ve score out of three (e.g. 0.75 + 1.0 + 0.75 = 2.5 out of 3 total). Above grade walls and below grade walls are evaluated on different scales, as they typically have significantly different construc ons (i.e. wood versus concrete). Note that the selec on of alterna ve materials and construc on prac ces may influence these ra ngs, as will the predicted service life.

Acceptable

Good

Excellent

Leaf 1: Materials and Construc on This leaf accounts for the environmental impacts of the ini al phase of a building assembly’s life-cycle, including producing the materials and construc ng the assemblies themselves. It accounts for factors such as primary resource harves ng and mining, transporta on of materials to the factory and building site, material waste, and the energy used to produce and install the materials.

This category was evaluated using Athena IE4B (see below).

Leaf 2: Ease of Modifica on During the service life of a wall assembly, it is likely that modifica ons to the original structure will be desired, whether due to a different desired aesthe c, a change in use of the building, or simply to provide addi onal space. This leaf provides an indica on of how easy it is to modify the assembly to accommodate changes to the building structure over its life, thereby facilita ng con nued use of the building. It takes into account aspects of construc on including the ease of material removal (i.e. spray foam versus board or baD products) as well as the complexity of the construc on. The performance of each assembly for this category was determined using a qualita ve evalua on based on experience with the materials and assemblies.

Leaf 3: End of Service Life At the end of the service life of a wall assembly, it is necessary to deconstruct the assembly and then safely dispose of its cons tuent materials. In some cases it may also be possible to reuse or recycle some or all of the materials in an assembly. This third leaf accounts for this phase of the wall assembly life-cycle including the environmental impacts associated with deconstruc on, transport of the waste materials, and disposal of the materials. This category was evaluated using Athena IE4B (see below).

Athena Impact Es mator for Buildings The Athena Impact Es mator for Buildings (Athena IE4B v.5.0.0105) is a life-cycle assessment soMware tool developed by the Athena Sustainable Materials Ins tute for the assessment of buildings and their assemblies. The tool provides a database of materials including the environmental impact associated with their produc on, installa on, maintenance, and disposal through the life-cycle of a building.

It includes considera on of a wide range of factors including global warming poten al, acidifica on poten al, human health par culates, ozone deple on poten al, smog poten al, and eutrophica on poten al. More informa on regarding the Athena Ins tute and a free download of IE4B (with registra on) are available at www.athenasmi.org.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Cladding Support & Fasteners Through Exterior Insula on This sec on provides an overview of the various cladding support systems commonly used with exterior insula on, and specific guidance for the design and construc on of cladding aDachment systems that incorporate screws through strapping and exterior insula on. The informa on is organized as follows: Cladding Support Op ons Structural Considera ons Installa on Methods Fastener Tables

Disclaimer and note on BCBC and VBBL compliance: The structural design guidance and the specific structural requirements given in this sec on are completed for wood-frame wall assembly types and cladding types (i.e. weights) as described in this sec on. Structural calcula ons and design was completed using standard engineering analysis and suppor ng tes ng informa on available in exis ng literature. The fastener and strapping requirements tables provided in this sec on can be referenced for the design and construc on of wood-frame wall assemblies where the cladding is supported on strapping fastened through exterior insula on. For wall assemblies that do not match the types and configura ons described in this sec on, addi onal resources and project specific structural design of the cladding aDachment would likely be required. The manufacturers of the cladding, insula on, and fastener products used for a specific project should be consulted to confirm the suitability of the product for wood-frame wall assemblies where the cladding is supported on strapping fastened through exterior insula on. Refer to the Addi onal Resources listed at the end of this guide for further structural design informa on.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Cladding Support Op ons

Cladding Support & Fasteners Through Exterior Insula on

OMen exterior insula on is required to achieve R-22 thermal performance, and the associated cladding aDachment and detailing may be new for some builders. In a conven onal wood-framed wall assembly, cladding is aDached either directly to the sheathing or over ver cal strapping1 fastened directly to the stud wall and wood sheathing. The addi on of exterior insula on increases the distance between the sheathing and the cladding, thus changing the loading which must be supported.

There are various approaches which can be used to support the cladding, and the selec on of a method oMen depends on the structural loads which must be accommodated. The amount of thermal bridging (i.e. reduc on in effec veness of the exterior insula on) associated with each of these methods varies, and is also an important considera on. In all cases, it is important that other aspects of assembly design including the provision of drainage be considered.

Fasteners Through Insula on: Cladding can be aDached and supported by ver cal strapping which is fastened with long screws through the exterior insula on and into the framed wall. This is in most cases the most thermally efficient mechanically fastened cladding support op on, as thermal bridging of the exterior insula on is limited to the fasteners through the insula on. The strapping also creates a drainage space, capillary break, and ven la on cavity (i.e. rainscreen cavity) which is consistent with effec ve moisture-management techniques. In this arrangement, the rigid exterior insula on and fasteners will act in tandem to carry the cladding load. Extruded polystyrene (XPS), expanded polystyrene (EPS), polyisocyanurate (polyiso), and rigid mineral fibre insula ons are suitable for this aDachment method. Given the prevalence of this system in low-rise residen al construc on, further guidance on structural cladding support using screws through insula on is provided in the following pages of this sec on.

Proprietary Thermally Efficient Spacers and Clips: Proprietary thermally efficient spacer and clip systems can be used to facilitate installa on and/or to support heavier claddings or resist larger wind loads. A number of systems exist, and selec on should be made based on the thermal efficiency of the spacers in combina on with the ability to support the required loads and accommodate the specified insula on thickness. Low conduc vity materials such as fiberglass and stainless steel can provide excellent thermal efficiency. These spacer and clips systems provide the addi onal benefit of facilita ng the use of semi-rigid (rather than rigid) insula on.

Con nuous Strapping or Wood Spacers: Cladding can also be supported using con nuous wood strapping which penetrates the exterior insula on, or alterna vely by standard strapping installed over wood spacers. When con nuous wood strapping is used, the reduc on of the thermal efficiency of the exterior insula on should be accounted for using a parallel paths approach, consistent with the approach for wood stud walls. Con nuous strapping and wood spacers can also provide the addi onal benefit of facilita ng the use of semi-rigid insula on, rather than rigid.

Masonry Ties: In cases where masonry cladding is used, masonry es are used to support the cladding in conjunc on with bearing of the masonry on lintels or a shelf angle, consistent with standard prac ce for this cladding type. These es can either be installed such that they penetrate the exterior insula on, or can be installed on the exterior face of thermally efficient spacer systems to reduce the thermal impact of the es.

Structural Adhesive: In some systems, such as Exterior Insulated Finish Systems (EIFS), structural adhesives can be used to aDach the exterior insula on and integrated cladding. An advantage of this system is that no structural elements must penetrate the insula on, so consequently there is essen ally no reduc on in the insula on effec veness. Historically moisture related issues have been experienced with face-sealed EIFS; however, adequate performance is achievable when installed using rainscreen principles including drainage behind the insula on and good detailing over a robust water resis ve barrier.

1

Note that for the purposes of this guide, the term “strapping” will be used to describe ver cal wood furring used to create a capillary break and ven la on space (i.e. rainscreen cavity).

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Structural Considera ons

Cladding Support & Fasteners Through Exterior Insula on

For systems using fasteners through exterior insula on, ver cal strapping on the front face of the exterior insula on is fastened with long screws through the insula on and into the framed wall. The cladding is then aDached and supported with separate fasteners through the strapping. The bending resistance from the screw (when installed into the sheathing and studs), coupled with a truss system, where the fasteners take tension loads, and the compression loads are resisted by the bearing of the strapping on the insula on layer, provide the primary support for the cladding in the service load state. Addi onally, the fric on between the insula on and the strapping and sheathed wall (created by the force applied by the fasteners) provides some resistance to the ver cal load, though it is generally not accounted for in the structural design. Insula on that is rigid enough to be used in this manner includes XPS, EPS, polyiso, and rigid mineral fibre products.

This cladding aDachment system can be used effec vely for claddings with weights up to 15 lbs/M² (73 kg/m²), excluding the weight of the insula on.

Within this limit, the screw size and installa on will vary depending on the cladding weight (see next page). Based on research and current industry prac ce it is recommended that claddings that weigh over 15 lbs/M² (73 kg/m²) be aDached using an engineered approach specific to the cladding type and weight. Though cladding weight will generally govern the structural support requirements on low-rise wood-frame buildings, the poten al forces generated by wind as well as seismic ac vity is also considered in the structural design to confirm these loads can be accommodated.

In addi on to cladding weight, the stud spacing of the backup wall, the sheathing type and thickness and the exterior insula on thickness and type will affect the required fastener spacing, size, minimum embedment into the backup wall, and the strapping thickness and width. Each factor must be considered in the design for the cladding aDachment on strapping with fasteners through exterior insula on. (Further discussion on next page.)

Lower density rigid and semi-rigid mineral fibre insula on (less than 8 lbs/M³, 126 kg/m³) is not considered rigid enough for this applica on and would likely compress excessively under the ver cal strapping during installa on.

Therefore, these products are not included in subsequent guidance on cladding aDachment with fasteners through exterior insula on in this sec on.

Addi onally, this structural system relies on the increased pullout strength of large screws as compared to nails. Nails are not recommended for use in this applica on unless designed by an engineer for a specific project.

Gravity

Tension Fric on Bending

Wind/ Seismic

Compression (Insula on)

Service Load State (Sec on View)

Page 11

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Cladding Support & Fasteners Through Exterior Insula on

Structural Considera ons (cont.)

Cladding Weight

Cladding weight for the purpose of the structural calcula ons included in this guide are categorized as Light (less than 5 lbs/M², 24kg/m²), Medium (5 to less than 10 lbs/M², 24–49 kg/m²), Heavy (10–15 lbs/M², 49–73 kg/m²), and Very Heavy (over 15 lbs/M², 73 kg/ m²) weight cladding. The approximate weight and category for various common cladding types is shown below. Each cladding type will have different weights for different brands and cladding arrangements, so the specific cladding weight should be determined from product technical data to confirm which category it is in.

Wood Siding Metal Panel Vinyl Siding Fibre Cement Siding

0 lbs/B²

Light Weight

Thin Concrete Panel

5 lbs/B² (24 kg/m²)

Medium Weight

Stucco

10 lbs/B² (49 kg/m²)

Thin Stone Veneer Thick Stone, Masonry, etc

Heavy Weight

15 lbs/B² (73 kg/m²)

Very Heavy Weight

Strapping In general, the most appropriate strapping for this applica on will be plywood strapping1 ripped to width, since the requirements for large screws at close spacing risk spliZng strapping made from dimension lumber, especially for thinner strapping. Addi onally, aMer the strapping is installed, more fasteners are installed through the strapping to secure the cladding. Larger dimension lumber strapping such as nominal 1x3 or nominal 1x4 may also be adequate in this applica on. The required strapping thickness and width for structural purposes is a func on of the cladding weight and insula on density. Thicker strapping may be necessary when used with rigid mineral wool products (compared to rigid foam) in order to reduce poten al bowing or twis ng of the strapping between fasteners as it is installed and as cladding is aDached. Wider strapping may be necessary to reduce the poten al compression of the insula on, especially for rigid mineral wool, by spreading the force of the fastener tension over more insula on area behind the wider strapping.

Strapping thickness and width should meet the minimum requirements given in the tables at the end of this sec on, though they are not constrained to the sizes given and can be wider and thicker where appropriate. For example, some cladding products may require a minimum fastener embedment that is thicker than the minimum strapping thickness given in the tables. Confirm with the cladding manufacturer the correct size and configura on of the strapping for the specific cladding products. Addi onally, refer to the code requirements for minimum strapping dimensions and spacing in Part 9 construc on (BCBC and VBBL 9.27.5).

Drain Mat For wall assemblies with light weight cladding and up to a maximum of 2” of exterior insula on, strapping may be replaced with an appropriate drain mat product on the front face of the exterior insula on. The drain mat is used to create the drained and vented cavity behind the cladding, and support the cladding aDachment. The cladding should be aDached with screw fasteners installed through the drain mat and insula on directly into the backup wall, with at least the same fastener spacing, size and embedment requirements as given for equivalent strapping applica ons (see tables), or as required by the cladding manufacturer. The drain mat product should have a minimum compression and s ffness strength to meet the forces expected from cladding aDachment and as required by the cladding manufacturer for an acceptable aDachment substrate. Refer to the specific product literature and manufacturer guidance for determining the suitability of the drain mat product for installa on in a rainscreen or ver cal drainage applica on. Note that this wall assembly may s ll require the use of wood strapping in order to support cladding and trim around windows or other penetra ons through the exterior insula on.

Some assemblies in other parts of this guide are shown with a thin drainage layer at the exterior of the sheathing membrane, such as would be provided by a grooved sheathing membrane product or grooved insula on. In most cases this layer is expected to have minimal thickness and is not considered to affect the structural requirements of the assembly. The requirements of the fastener tables can be applied to assemblies with these components. For assemblies that include an actual drain mat in this configura on, the same structural requirements would apply as for drain mat used at the front face of the exterior insula on, as described above.

1

Borate treatments are oMen suitable for wood strapping, and are recommended for most applica ons. Alkaline copper quat (ACQ) and chromated copper arsenate (CCA) may also be suitable wood treatments, though compa bility with fasteners and adjacent metals should be considered.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Structural Considera ons (cont.)

Cladding Support & Fasteners Through Exterior Insula on

Screws Screws used to aDach the strapping through the insula on should be either stainless steel or galvanized steel with a coa ng rated to 2000 hour salt spray per ASTM B117, as they will be exposed to the exterior environment and should be protected from corrosion to ensure long term durability. Addi onal resistance may be required in highly corrosive environments. Always ensure the screw type is compa ble with both the strapping material (i.e. wood pressure treatment) and the cladding material1. This applica on may require specialty screws designed to accommodate the poten ally large torque expected as they are installed through thick layers of insula on and into the backup wall. One important constructability considera on is the use of screws with a countersunk head so that the screw head can be embedded into the front face of the strapping and out of the way of cladding materials and aDachment accessories.

Backup Wall and Minimum Fastener Embedment The stud spacing of the exterior framed wall will govern the horizontal spacing of the strapping and fasteners, as all fasteners through exterior insula on must be installed through the exterior sheathing into studs. Closer stud and strapping horizontal spacing (i.e. maximum 16” o.c.) provides addi onal support of the cladding, and therefore may allow less frequent ver cal screw placement. For wider spaced framing (i.e. 24” o.c. horizontal spacing) closer ver cal spacing of screws may be required (see tables).

The structural design included in this sec on assumes all of the screws used to fasten the strapping in place are installed through wood sheathing and into the wood framing in the backup wall2, and standard plywood or oriented strand board sheathing is used as the sheathing material. For ease of construc on, consider using markers or snap lines on the outside face of the wall sheathing membrane in line with the stud framing in order to clearly indicate the correct loca on of screws into the backup wall. Note that screws that uninten onally miss the framing should not be removed for reposi oning, as the hole created in the sheathing membrane by the screw may introduce a risk or water ingress and/or air leakage in the wall assembly. Screws should be leM in place, with a secondary screw installed as close as possible into the stud.

The minimum embedment length as given in the tables is measured from the outside face of the wood sheathing. BCBC and VBBL code requirements for the minimum embedment of cladding aDachment fasteners (9.27.5.7) dictate that the fasteners must at least fully penetrate through the exterior sheathing, and therefore the tables include a minimum fastener embedment of 1”, to account for up to 3/4” exterior sheathing. Addi onally, minimum embedment length only accounts for the non-tapered por on of the screw where the screws threads are at the full diameter, and does not include the p of the screw. As a rule of thumb, approximately the front 1/4” of the screw should be ignored in determining the appropriate screw length. Contact the screw manufacturer for further informa on.

1

Stainless steel fasteners should be used when using ACQ treated wood, and either stainless steel or galvanized steel fasteners can be used when using Borate or CCA treated wood. Cau on should be exercised when using aluminum based materials in conjunc on with copper based wood treatments such as ACQ and CCA. For further informa on refer to the Builder Insight #8 - Compa bility of Fasteners and Connectors with Residen al Pressure Treated Wood, published by BC Housing.

2 Note that specific structural design can be completed for an assembly where fasteners are supported only by the sheathing, though this design approach is not included in this guide.

Page 13

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Structural Considera ons (cont.)

Cladding Support & Fasteners Through Exterior Insula on

Deflec on Tes ng has shown that some minor deflec on of the strapping and cladding may be experienced for wall assemblies with heavy weight claddings. In most cases, the deflec on is constrained to less than 1/32” for typical heavy weight cladding loads. Claddings that may be prone to cracking such as stucco or adhered stone should be installed so as to reduce con nuous inside corners and irregular shapes, and wherever possible should be segmented into smaller areas across the face of the wall assembly using crack control joints. Refer to the Addi onal Resources listed at the end of this guide for further structural design and tes ng informa on.

Poten al deflec on for heavy weight cladding may be reduced by using deflec on blocks at the top of the strapping pieces, or by installing screws at an upwards angle into the backup wall. The approach with deflec on blocks uses pressure treated dimension lumber blocking, installed at the top of the strapping either at the rim joist or at the top of the wall, in order to “hang” the strapping (see illustra on). This provides a solid wood support mechanism and minimizes the deflec on movement of the cladding. Note that the blocking aDachment should be designed to provide 100% of the ver cal support for the cladding in order prevent ver cal loading on the screws at por ons of the strapping without deflec on blocks. In addi on to ver cal deflec on, this approach can also serve to minimize over- ghtening of the screws laterally through exterior insula on. The structural design in this sec on does not account for installa on of deflec on blocks at the top of the strapping, and therefore specific structural design should be completed for wall assemblies where this configura on is desired.

Where screws are installed at an upward angle, the support system will rely more readily on the truss ac on of the screw tension and insula on compression, rather than screw bending resistance. Therefore, the poten al for deflec on that may occur from suppor ng heavy weight cladding on the strapping is reduced. Note that screws installed at an upwards angle may need to be longer than those used horizontally as they must achieve the same embedment in the backup wall. The structural design in this sec on does not account for screws being installed at an upwards angle and therefore specific structural design should be completed for wall assemblies where this configura on is to be used.

Sec on View

Deflec on Block

Page 14

Screw at Upward Angle

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Installa on Methods

Cladding Support & Fasteners Through Exterior Insula on

Insula on Boards Installa on of one or mul ple layers of exterior insula on requires a stepped approach, as each insula on board should be aDached using only the strapping as much as possible, so as to reduce the number of fastener penetra ons through the insula on and sheathing membrane. This approach is most easily completed using the following installa on procedure (see illustra on): 1.

2.

3.

Install the starter course of insula on using the strapping fastened at the boDom edge and held upright in place as needed. Insula on boards should be installed with the ver cal edges offset 8” from the strapping so that each board (usually 48” wide) will be secured behind 3 separate straps.

Place the insula on behind the strapping and “stack” it on the starter course, with screws installed along the strapping through the insula on boards as they are installed up to the top edge.

16”

8”

3 2 1

Insula on boards in a single layer can be stacked directly above the course below or offset horizontally, and should be offset 16” horizontally between layers if mul ple insula on layers are used.

An alterna ve installa on approach is to use one or two fasteners to pin the insula on boards in place before the strapping is installed.

This approach may require screws with large washers to adequately secure heavier insula on. Refer to the insula on manufacturer product data for further guidance on fastener layout and installa on requirements.

Con nuity of Insula on Boards should be installed in as large as possible pieces over the wall area. Pieces can be cut aMer installa on to ensure all wall surfaces, including around openings and penetra ons, are covered while minimizing gaps and insula on board joints. Mul ple layers of insula on should be used when possible, with joints staggered to reduce thermal bypass at the insula on. Exterior insula on should only be interrupted by necessary service penetra ons and structural elements. Cladding accessories such as trim and flashings should be installed in front of the insula on where possible. For example consider installing the back face of through-wall flashings onto a small strip or intermiDent pieces of pressure treated lumber in the plane of the insula on (see illustra on), instead of installing the flashing at the face of the sheathing. Self-adhered membrane can be used instead of the metal flashing material to divert water out from the sheathing membrane as required.

Rain Screen Free Area The BCBC and VBBL codes require that rainscreen cavi es have a minimum free area of 80% (9.27.2), meaning that material used to create the space must not exceed 20% of the cross-sec onal area of the drained and vented cavity. This requirement can generally be met with most strapping arrangements, including the strapping widths given in the tables at the end of this sec on. However, at details or termina ons wherever addi onal insula on or cladding support is necessary, narrower strapping or intermiDent pieces should be used as infill for wall assemblies where 3” wide strapping is used, in order to maintain the 80% free area.

Drain mat products used to create the rainscreen cavity must also provide a minimum 80% open cavity area, and the design and installa on should also account for poten al compression into the front face of the insula on due to the fastener tension. The Authority Having Jurisdic on should be no fied to confirm that the arrangement of the drained and vented cavity is acceptable.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Cladding Support & Fasteners Through Exterior Insula on

Fastener Tables

The following pages include the structural requirements for aDaching strapping over exterior insula on using long screws. The tables are organized by cladding weight, with fastener requirements shown for insula on thicknesses up to 8”. Illustra ons of each aspect of the fastener and strapping installa on requirements are shown below. See the documents listed in the Addi onal Resources sec on of this guide for more guidance and specific calcula on examples for the structural design of cladding support using fasteners through exterior insula on, and for guidance on systems that use more than 8” of exterior insula on.

Stud Framing (16”/24” o.c.)

Plan View

Maximum Ver cal Screw Spacing

Sec on View

Minimum Strapping Size (Thickness x Width)

Minimum Screw Size Number

Minimum Screw Embedment (through wood sheathing and into wood studs, discoun ng screw p)

Insula on thickness (Rigid Foam/Rigid Mineral Wool)

The table below outlines the assumed structural proper es for the materials used in this cladding support system.

Assumed Structural Proper es Rigid foam minimum compressive strength

Rigid mineral wool minimum compressive strength

1440 psf (69 kPa)

439psf (21kPa)

@ 10% compression, ASTM C165 tes ng

@ 10% compression, ASTM C165 tes ng

Page 16

Stainless/galvanized steel screw allowable tensile strength 60,000 psi (414 MPa)

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Cladding Support & Fasteners Through Exterior Insula on

Fastener Tables (cont.)

Light Weight Cladding

Fastener/Strapping Installa on Requirements—Light Weight Cladding Thickness of Maximum Minimum Minimum Exterior Ver cal Screw Screw Screw Size Insula on Spacing Embedment

Minimum Strapping Size Rigid Foam

Rigid Mineral Wool

Light Weight Cladding Below 5 lbs/B² - 16” o.c. Stud Framing 1” to 2”

*

>2” to 8”

24” 16”

#10

1”

3/8” x 1-1/2”

3/8” x 2-1/2”

Light Weight Cladding Below 5 lbs/B² - 24” o.c. Stud Framing 1” to 2” * >2” to 8”

16” 12”

#10

1”

3/8” x 2-1/2”

3/8” x 2-1/2”

*Wall assemblies with light weight cladding and up to 2” of exterior insula on may use a drain mat rainscreen product in lieu of strapping where appropriate, with fasteners aDached directly to the wall framing.

Appropriateness of products and fastening configura ons in this applica on to be confirmed with drain mat manufacturer and cladding manufacturer. This approach is unlikely to be suitable for insula on thickness greater than 2”, or for heavier claddings.

Medium Weight Cladding Fastener/Strapping Installa on Requirements—Medium Weight Cladding Thickness of Maximum Minimum Minimum Exterior Ver cal Screw Screw Screw Size Insula on Spacing Embedment

Minimum Strapping Size Rigid Foam

Rigid Mineral Wool

Medium Weight Cladding Between 5 lbs/B² and 10 lbs/B² - 16” o.c. Stud Framing 1” to 4”

16”

>4” to 8”

12”

#12

1”

1/2” x 2-1/2”

1/2” x 3”

Medium Weight Cladding Between 5 lbs/B² and 10 lbs/B² - 24” o.c. Stud Framing 1” to 4”

12”

>4” to 8”

8”

#12

1”

1/2” x 2-1/2”

1/2” x 3”

Heavy Weight Cladding Fastener/Strapping Installa on Requirements—Heavy Weight Cladding Thickness of Maximum Minimum Minimum Exterior Ver cal Screw Screw Screw Size Insula on Spacing Embedment

Minimum Strapping Size Rigid Foam

Rigid Mineral Wool

Heavy Weight Cladding Between 10 lbs/B² and 15 lbs/B² - 16” o.c. Stud Framing 1” to 2”

16”

>2” to 8”

12”

#14

1-1/2”

1/2” x 3”

3/4” x 3”

Heavy Weight Cladding Between 10 lbs/B² and 15 lbs/B² - 24” o.c. Stud Framing 1” to 2”

10”

>2” to 4”

8”

>4” to 8”

6”

#14

1-1/2”

1/2” x 3”

3/4” x 3”

Page 17

Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls This sec on provides informa on about four dierent above grade wall assemblies that can achieve the R-22 thermal performance target: Split Insulated Walls Exterior Insulated Walls Double Stud Walls Deep Stud Walls with Service Wall

Page 18

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Split Insulated Walls This above grade wall assembly consists of rigid or semi-rigid insula on placed on the exterior of a conven onal above grade, insulated 2x4 or 2x6, wood-frame wall assembly. High effec ve R-values of the assembly are achieved by using con nuous insula on outside of the structural framing and thermally efficient cladding aDachments, in combina on with insula on in the stud space. In most cases, cladding can be supported by strapping fastened with screws through rigid insula on (see previous sec on). It is also possible to use thermally efficient cladding aDachment systems. The exterior insula on product used in this arrangement should not be sensi ve to moisture as it will be exposed to periodic weZng. In cold climates, insula on placed on the exterior of the stud wall increases the temperature of the moisture-sensi ve wood sheathing and framing and consequently oMen improves the durability of the assembly by reducing the risk of condensa on and associated moisture damage.

Exterior Cladding 1x3 Strapping (Ven lated Airspace) Exterior Insula on (Rigid Mineral Wool) Vapour Permeable Sheathing Membrane Sheathing (Plywood) 2x6 Wood Studs w/ BaP Insula on (Fiberglass) Vapour Barrier (Polyethylene Sheet) Gypsum Wall Board Interior

Key Considera ons: The method of cladding aDachment is important to limit thermal bridging through the exterior insula on while adequately suppor ng the exterior cladding (see previous sec on).

The vapour permeability of the sheathing membrane and exterior insula on should be carefully considered so as not to create a risk of condensa on within the assembly, or to intolerably reduce the ability of the assembly to dry in the event that incidental weZng occurs.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Split Insulated Walls (cont.)

Cladding Any type of cladding can be used with this wall assembly. The selec on of the cladding aDachment strategy will depend on the weight and support requirements of the cladding. In many cases, the cladding can simply be aDached to ver cal 1x3 strapping (or similar) fastened through the exterior insula on and into the backup wall. In this arrangement, the rigid exterior insula on and fasteners will act in tandem to carry the cladding load (see previous sec on). Thermally efficient cladding supports and brick es can also be used with this assembly and would permit the use of semi-rigid exterior insula on products.

Water Resis ve Barrier A vapour-permeable sheathing membrane should be installed on the exterior of the wall sheathing, behind the exterior insula on. There are a variety of both loose (i.e. mechanically fastened) and selfadhered sheet products, as well as some liquid applied products that can be used in this applica on.

The sheathing membrane should be vapour-permeable so as to facilitate some outward drying of the assembly. Where rela vely impermeable foam insula on is used on the exterior, joints should be taped and sealed so that water does not penetrate through the insula on and poten ally become trapped in the wall assembly. (Further discussion on next page.)

Air Barrier This assembly can accommodate several air-barrier strategies; however, oMen the most straighVorward is to use the sheathing membrane. If the sheathing membrane is to form the air barrier, it must be taped and sealed to ensure con nuity. Structural support of the sheathing membrane is provided by the sandwiching of the insula on and sheathing on either side. Alterna vely, a sealed sheathing approach can be used, or poten ally air ght polyethylene on the interior of the stud wall or air ght drywall, though ensuring con nuity of the laDer approaches can be arduous. Con nuity of the air barrier at transi ons and penetra ons is cri cal to its performance.

Vapour Barrier The exterior insula on in this assembly increases the temperature of the sheathing and reduces the poten al for condensa on; however, a vapour barrier should s ll be installed on the interior of the stud wall unless the majority of insula on R-value is placed on the exterior of the sheathing. Typically, a polyethylene sheet is used as the interior vapour barrier in these types of assemblies, though other op ons including vapour barrier paint or smart vapour retarder sheet products may be appropriate. If sufficient exterior insula on is installed a more permeable op ons such as latex paint may be adequate. These more permeable op ons may be desirable if rela vely impermeable exterior insula on products are used.

(Further discussion on following pages.)

Effec ve Assembly R-value of Split Insulated Wall Assembly [B²•°F•hr/Btu] 2x4 Stud Wall (R-12 BaPs)

2x6 Stud Wall (R-19 BaPs)

R-value/inch of Exterior Insula on

Thickness of Exterior Insula on

R-4.0

R-5.0

R-4.0

R-5.0

0”

11.3

11.3

16.2

16.2

1/2”

13.3

13.8

18.2

18.7

1”

15.3

16.3

20.2

21.2

1 1/2”

17.3

18.8

22.2

23.7

2”

19.3

21.3

24.2

26.2

2 1/2”

21.3

23.8

26.2

28.7

3”

23.3

26.3

28.2

31.2

3 1/2”

25.3

28.8

30.2

33.7

4”

27.3

31.3

32.2

36.2

4 1/2”

29.3

33.8

34.2

38.7

5”

31.3

36.3

36.2

41.2

5 1/2”

33.3

38.8

38.2

43.7

6”

35.3

41.3

40.2

46.2

A 23% framing factor is assumed which is consistent with standard 16” o.c. stud framing prac ces.

R-values below the R-22 requirement

Page 20

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Split Insulated Walls (cont.)

Above Grade Walls

Interior Insula on Types The stud space can be insulated using a variety of different insula on types, including baDs (i.e. mineral wool or fiberglass), blown-in fibrous insula on (i.e. cellulose or fiberglass), or open-cell spray foam1. With fibrous fill insula ons, higher density blown products with integral binders can be used to prevent seDlement. A combina on of closed-cell spray foam and fibrous fill in a flash-and-fill applica on could also be considered to improve air ghtness of the assembly and also reduce convec ve looping due to voids within the insula on between the studs.

Environmental Considera ons Split insulated walls typically have a rela vely low environmental impact due to the limited material usage and ease of modifica on. The 2.5 ra ng provided for this assembly is the same regardless of the selected exterior insula on type as shown below. However, when closed-cell spray foam is used in the stud cavity instead of baDs, the ra ng is significantly decreased. This decrease is in part due to the significant effort required to remove spray foam from the stud cavi es to allow for modifica ons.

Mineral Wool Exterior Insula on

EPS Exterior Insula on

Closed-Cell Spray Foam in Stud Cavity with Mineral Wool Exterior Insula on

XPS Exterior Insula on

Polyiso Exterior Insula on

Other Considera ons When installing insula on on the exterior of the sheathing, typically wider strapping is used to distribute the cladding load to a wider area of the insula on and avoid compression of the insula on. Either preserva ve-treated dimension lumber or preserva ve-treated plywood strapping can be used in this applica on. Care should be taken to ensure that the necessary ven la on area is maintained when using wider strapping. Compa bility of fasteners with the strapping wood treatment should also be considered. See the previous sec on for detailed informa on on the structural requirements for cladding support and fasteners through exterior insula on.

1

Note that open-cell (low density) spray-foam is not explicitly included as an acceptable insula on type in the BCBC 2012 and VBBL 2014, but it is well-used in the building industry and for the purpose of this guide is considered an appropriate insula on material. As with all solu ons provided in this guide, its use should be confirmed as acceptable with the local Authority Having Jurisdic on.

Page 21

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Split Insulated Walls (cont.)

Exterior Insula on Types & Considera ons

Various types of exterior insula on can poten ally be used in split insulated wall assemblies, including permeable insula ons such as semi-rigid or rigid mineral wool, or semi-rigid fiberglass, and rela vely impermeable insula ons such as extruded polystyrene (XPS), expanded polystyrene (EPS), polyisocyanurate (polyiso), and closed-cell spray polyurethane foam. While each of these insula on materials can provide adequate thermal resistance, the permeability of the materials is of par cular importance with respect to the drying capacity of the wall assembly. A rela vely impermeable foam plas c insula on will not readily allow for moisture in the wall to dry outwards. If this insula on is installed in conjunc on with an interior vapour barrier (i.e. polyethylene sheet), the two vapour barriers can trap moisture that inadvertently gets into the assembly and can poten ally lead to fungal growth and decay.

To avoid this situa on, when impermeable insula on is used, the ra o of insula on outboard of the sheathing to insula on in the stud cavity should be carefully considered so as to maintain the temperature of the sheathing at rela vely safe levels and avoid condensa on. Addi onally, while not explicitly required by the codes, a rela vely more permeable interior vapour barrier such as a smart vapour retarder or vapour retarder paint could be used to permit some amount of inward drying. A thin drainage layer could also be included at the exterior of the sheathing membrane to facilitate drainage of any water which may penetrate behind the insula on. In general, a vapour permeable exterior insula on in combina on with an interior vapour barrier typically provides a lower risk wall assembly than does an assembly using impermeable exterior insula on.

Code Compliance Paths for Split Insulated Wall Assemblies

Rela vely Permeable Exterior Insula on (> 60 ng/(s•m²•Pa))

Exterior-to-Interior Insula on Ra o (Table 9.25.5.2)

Using permeable exterior insula on (defined by code as > 60 ng/(s•m²•Pa)) does not trigger the requirements regarding placement of impermeable insula on products and consequently can comply with code. When using this approach it is important to consider the thickness of the insula on in determining its permeance. When exterior insula on with permeance rela vely close to the code limit is used, it may be prudent to use a rela vely permeable interior vapour barrier such as a smart vapour retarder or vapour retarder paint, as well as a drainage layer behind the insula on such as grooved sheathing membrane.

When impermeable exterior insula on is used, the wall can comply by mee ng the insula on ra o requirements of Table 9.25.5.2 which are intended to limit the poten al for condensa on within the wall assembly.

Since outward drying in these assemblies is limited by the impermeable insula on, it may be prudent to use a rela vely permeable interior vapour barrier such as a smart vapour retarder or vapour retarder paint, as well as a drainage layer behind the insula on such as grooved sheathing membrane. The exterior-to-interior insula on ra o can also be taken to an extreme such that only exterior insula on is used.

Page 22

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Exterior Insulated Walls This above grade wall assembly consists of rigid or semi-rigid insula on placed on the exterior of a conven onal above grade, uninsulated 2x4 or 2x6, wood-frame wall assembly. High effec ve R-values of the assembly are achieved by using con nuous insula on outside of the structural framing in combina on with thermally efficient cladding aDachments. In most cases cladding can be supported by strapping fastened with screws through rigid insula on (see previous sec on). It also possible to use thermally efficient cladding aDachment systems. The exterior insula on product used in this arrangement should not be sensi ve to moisture as it will be exposed some periodic weZng. In cold climates, insula on placed on the exterior of the stud wall increases the temperature of the moisture-sensi ve wood sheathing and framing and consequently oMen improves the durability of the assembly by reducing the risk of condensa on and associated moisture damage.

Exterior Cladding 1x3 Strapping (Ven lated Airspace) Exterior Insula on (Extruded Polystyrene) Sheathing Membrane Sheathing (Plywood) 2x4 Wood Studs (empty cavity) Gypsum Wall Board Interior

Key Considera ons: The method of cladding aDachment is important to limit thermal bridging through the exterior insula on while adequately suppor ng the exterior cladding (see previous sec on).

Since in this assembly the insula on is located en rely outside the framed wall, the typically used interior vapour barrier (i.e. polyethylene sheet, vapour barrier paint, etc.) should be removed.

Vapour impermeable sheathing membrane can be used to provide both liquid water and vapour control (i.e. water resis ve barrier and vapour barrier).

Page 23

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Exterior Insulated Walls (cont.)

Cladding Any type of cladding can be used with this wall assembly. The selec on of the cladding aDachment strategy will depend on the weight and support requirements of the cladding. In many cases the cladding can simply be aDached to ver cal 1x3 strapping (or similar) fastened with screws through the exterior insula on and into the backup wall. In this arrangement, the rigid exterior insula on and fasteners will act in tandem to carry the cladding load (see previous sec on). Thermally efficient cladding supports and brick es can also be used with this assembly and would permit the use of semi-rigid exterior insula on products.

Water Resis ve Barrier A vapour-impermeable sheathing membrane should be installed on the exterior of the wall sheathing, behind the exterior insula on, to provide the water resis ve barrier for this assembly. Typically a self-adhered sheet product is appropriate for this applica on, and some liquid applied products can also be used. Where rela vely impermeable foam insula on is used on the exterior, joints should be taped and sealed so that water does not penetrate through the insula on and poten ally become trapped in the wall assembly.

While an impermeable membrane oMen provides the lowest risk and most easily constructed assembly, it is also possible to use a vapour permeable sheathing membrane in this assembly, though it is important that drainage be provided between the insula on and sheathing membrane in this arrangement.

Air Barrier The most straighVorward air barrier approach for this assembly is to use the self-adhered sheathing membrane. If a mechanically fastened sheathing membrane is used, it must be taped and sealed to ensure con nuity. Structural support of a mechanically fastened sheathing membrane is provided by the sandwiching of the insula on and sheathing on either side. Alterna vely, a sealed sheathing approach can be used. Con nuity of the airbarrier at transi ons and penetra ons is cri cal to its performance.

Effec ve Assembly R-value for 2x4 or 2x6 Exterior Insulated Stud Wall (No BaPs) [B²•°F•hr/Btu] Thickness of Exterior Insula on

R-value/inch of Exterior Insula on R-4.0

R-5.0

3 1/2”

17.8

21.3

4”

19.8

23.8

4 1/2”

21.8

26.3

5”

23.8

28.8

5 1/2”

25.8

31.3

6”

27.8

33.8

6 1/2”

29.8

36.3

7”

31.8

38.8

Exterior Insula on Types Various types of exterior insula on can poten ally be used in this assembly including permeable insula ons such as semi-rigid or rigid mineral wool, or semi-rigid fiberglass, and rela vely impermeable insula ons such as extruded polystyrene (XPS), expanded polystyrene (EPS), polyisocyanurate (polyiso), and closed-cell spray polyurethane foam.

Vapour Barrier The exterior insula on in this assembly increases the temperature of the sheathing and nearly eliminates the poten al for damage associated with condensa on on the framing.

Rela vely impermeable sheathing membranes can be used as the vapour barrier in this assembly, and help limit the poten al for inward vapour drive from incidental water trapped between the insula on and the sheathing membrane. A vapour barrier should not be installed to the interior of the exterior sheathing. (i.e. polyethylene sheet).

R-values below the R-22 requirement

Note on Using Impermeable Materials Outside Wood-frame Walls There may be a risk of trapping exis ng construc on moisture in the wall assembly at wood stud packs and window headers if vapour-impermeable materials are used at the exterior face of the wood frame wall, since moisture will not easily dry inwards due to the wood thickness. To reduce this risk, always check that the wood is dry prior to installing impermeable membranes or insula on products, or consider using permeable materials in the exterior insulated wall assembly.

Page 24

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Double Stud Walls This above grade wall assembly consists of a deeper stud cavity created by an addi onal framed wall installed to the interior of a conven onal wood-frame wall. High effec ve R-values of the assembly are achieved by filling the increased cavity depth with either baD insula on, blown-in fibrous insula on, or spray foam insula on. There is no exterior insula on installed in this assembly, so cladding can be aDached directly to the wall through ver cal strapping (i.e. furring) using standard rainscreen detailing. In cold climates, the addi onal depth of insula on installed on the interior side of the exterior sheathing can slightly decrease the sheathing temperature and consequently increase the risk of condensa on on the moisture-sensi ve wood sheathing and framing. As a result, con nuity of the air barrier and installa on of an interior vapour barrier are cri cal to the performance of this assembly, as is the quality of the insula on installa on to reduce airflow within the assembly (i.e. convec ve looping).

Exterior Cladding Strapping (Ven lated Airspace) Sheathing Membrane Sheathing (Plywood) Double Stud Wall with Insula on (Cellulose with suppor ng neUng for installa on) Vapour Barrier (Polyethylene Sheet) Gypsum Wall Board Interior

Key Considera ons: The quality of the insula on installa on is cri cal to limi ng convec ve looping within the increased wall assembly depth which can reduce the effec veness of the insula on and also contribute to moisture accumula on within the assembly.

Con nuity of the air barrier and installa on of an interior vapour barrier are fundamental to the performance of this assembly as the slightly decreased exterior sheathing temperature (as compared to standard construc on) increases the risk of condensa on and related damage.

Page 25

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Double Stud Walls (cont.)

Cladding Any type of cladding can be used with this wall assembly and can be fastened directly to the wall using ver cal strapping (i.e. furring) and standard rainscreen details. The cladding is intended to control the majority of bulk water, and any water that does penetrate past the cladding must be able to drain out via the cavity created by the ver cal strapping.

Water Resis ve Barrier A vapour-permeable sheathing membrane should be installed on the exterior of the wall sheathing, behind the ver cal strapping. There are a variety of both loose (i.e. mechanically fastened) and selfadhered sheet products, as well as some liquid applied products which can be used in this applica on.

The sheathing membrane should be vapour-permeable to facilitate some outward drying of the assembly.

Air Barrier This assembly can accommodate several air-barrier strategies; however, oMen the most straighVorward is to use the sheathing membrane. If the sheathing membrane is to form the air barrier, it must be taped and sealed to ensure con nuity. Structural support of the sheathing membrane is provided by sandwiching between the ver cal strapping and sheathing on either side, or else through adhesion to the sheathing. Alterna vely, a sealed sheathing approach can be used for the air barrier. In this approach, joints in the sheathing must be taped and sealed.

Due to the significant depth of the insulated space, an interior layer (i.e. polyethylene sheet or drywall) should also be detailed as air ght to provide a secondary air barrier to prevent flow of air into the insulated cavity from the interior and reduce the poten al for convec ve looping.

Insula on Types The stud space can be insulated using a variety of different insula on types including baD (i.e. mineral wool or fiberglass), blown-in fibrous insula on (i.e. cellulose or fiberglass), or open-cell spray foam. With fibrous fill insula ons, higher density blown products with integral binders can be used to prevent seDlement within the deep wall cavity. A combina on of closed-cell spray foam and fibrous fill in a flash-and-fill applica on could also be considered to improve air ghtness of the assembly and also reduce convec ve looping within the insula on between the studs.

Vapour Barrier The rela vely large amount of insula on installed to the interior of moisture-sensi ve wood framing and sheathing increases the risk of moisture accumula on within this assembly. To control the outward flow of water vapour through this assembly an interior vapour barrier should be installed on the interior of innermost stud wall. Typically a polyethylene sheet is used as the interior vapour barrier in these types of assemblies, though other op ons including vapour barrier paint may be appropriate.

Other Considera ons In some cases, the studs of the interior framed wall are staggered rela ve to the exterior studs. By staggering the studs, the thermal bridging of the studs is slightly reduced; however, the R-value calcula on method (i.e. isothermal planes) does not provide a benefit for this stagger. Typically the R-value benefit of staggering the studs is minimal once separated by at least one inch.

Page 26

Effec ve Assembly R-value for Double 2x4 Stud Wall* [B²•°F•hr/Btu] R-value/inch of Insula on

Thickness of Gap Between Stud Walls

R-3.4

R-4.0

R-5.0

0”

19.7

21.2

23.3

1/2”

21.4

23.2

25.8

1”

23.1

25.2

28.3

1 1/2”

24.8

27.2

30.8

2”

26.5

29.2

33.3

2 1/2”

28.2

31.2

35.8

3”

29.9

33.2

38.3

3 1/2”

31.6

35.2

40.8

4”

33.3

37.2

43.3

4 1/2”

35.0

39.2

45.8

5”

36.7

41.2

48.3

*Assumes interior stud wall has same framing factor (23%) as exterior stud wall; however, less framing may be necessary since wall may be non-structural.

R-values below the R-22 requirement

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Deep Stud Walls with Service Wall This above grade wall assembly consists of a deeper stud cavity created using either deep studs (2x10, 2x12) or engineered wood I-joists and an addi onal 2x4 service wall constructed on the interior to allow for running of electrical, plumbing, and HVAC services without penetra ng the interior air barrier. These wall types will typically need to be engineered. High effec ve R-values of the assembly are achieved by filling the increased cavity depth with either baD insula on, blown-in fibrous insula on, or spray foam insula on. There is oMen no exterior insula on installed in this assembly, so cladding can be aDached directly to the wall through ver cal strapping (i.e. furring) using standard rainscreen detailing. In cold climates, the addi onal depth of insula on installed on the interior side of the exterior sheathing can slightly decrease the sheathing temperature and consequently increase the risk of condensa on. As a result, con nuity of the air barrier and installa on of an interior vapour barrier are cri cal to the performance of this assembly, as is the quality of the insula on installa on to reduce airflow within the assembly (i.e. convec ve looping).

Exterior Tape at Joints in Interior Plywood Sheathing

Cladding Strapping (Ven lated Airspace) Sheathing Membrane Sheathing (Plywood) Deep Stud Wall (Engineered Wood I-Joist) with Insula on (Fibreglass BaPs) Interior Plywood Sheathing 2x4 Framed Wall Gypsum Wall Board Interior

Key Considera ons: The quality of the insula on installa on is cri cal to limi ng convec ve looping within the increased wall assembly depth which can reduce the effec veness of the insula on and also contribute to moisture accumula on within the assembly.

Con nuity of the air barrier and installa on of an interior vapour barrier are fundamental to the performance of this assembly, as the slightly decreased exterior sheathing temperature (as compared to standard construc on) increases the risk of condensa on and related damage.

Page 27

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Above Grade Walls

Deep Stud Walls with Service Wall (cont.)

Cladding Any type of cladding can be used with this wall assembly and can be fastened directly to the wall using ver cal strapping (i.e. furring) and standard rainscreen details. The cladding is intended to control the majority of bulk water, and any water that does penetrate past the cladding must be able to drain out via the cavity created by the ver cal strapping.

Water Resis ve Barrier A vapour-permeable sheathing membrane should be installed on the exterior of the wall sheathing, behind the ver cal strapping. There are a variety of both loose (i.e. mechanically fastened) and self-adhered sheet products, as well as some liquid applied products that can be used in this applica on. The sheathing membrane should be vapour-permeable so as to facilitate some outward drying of the assembly.

Air Barrier

The interior sheathing between the service wall and deep stud (or engineered wood I-joist) wall should be detailed as air ght to provide the air barrier for this assembly.

This interior air barrier will prevent the flow of air into the insulated cavity from the interior as well as reduce the poten al for convec ve looping. In addi on to the interior air barrier, a secondary exterior air barrier such as a vapour permeable selfadhered sheathing membrane or sealed sheathing can also be used to Effec ve Assembly R-value for Deep Stud Walls reduce wind penetra on and improve the overall assembly air ghtness.

[B²•°F•hr/Btu] Insula on Types The stud space can be insulated using a variety of different insula on types including baD (i.e. mineral wool or fiberglass), blown-in fibrous insula on (i.e. cellulose), or open-cell spray foam. With fibrous fill insula ons, higher density blown products with integral binders can be used to prevent seDlement within the deep wall cavity. A cost effec ve combina on of opencell spray foam and fibrous fill in a flash and fill applica on could also be considered to improve air ghtness of the assembly and also reduce convec ve looping within the insula on between the studs.

The service wall stud space can either be leM empty, or it can be insulated to increase the assembly R-value.

Framing Type

Uninsulated Wood-Frame Service Wall

Insulated (R-12) 2x4 Service Wall

R-value/inch of Insula on

R-value/inch of Insula on

R-3.4 R-4.0 R-5.0 R-3.4 R-4.0 R-5.0

2x6

17.7

18.9

20.5

25.2

26.3

28.0

2x8

21.9

23.5

25.6

29.4

31.0

33.1

2x10

26.7

28.7

31.5

34.2

36.2

39.0

Note specifically that some 2x8 framed wall assemblies will achieve R-22 thermal performance, while others will not. Achieving R-22 with this type of framing will depend primarily on the R-value per inch of the insula on, the framing factor, the presence of a service wall, and the cladding type.

2x12

31.6

34.0

37.3

39.0

41.5

44.8

8” EWI*

24.0

26.2

29.6

31.4

33.7

37.1

Vapour Barrier

10” EWI

29.9

32.9

37.5

37.3

40.4

45.0

12” EWI

35.8

39.6

45.4

43.2

47.1

52.8

14” EWI

41.7

46.3

53.3

49.1

53.8

60.7

16” EWI

47.6

53.0

61.1

55.0

60.5

68.6

The rela vely large amount of insula on installed to the interior of the sheathing increases the risk of moisture accumula on within this assembly.

An interior vapour barrier should be installed on the interior of deep stud or engineered wood I-joist walls to control the outward flow of water vapour through this assembly. Plywood or OSB can be used as the interior vapour barrier in these types of assemblies.

1

A 23% framing factor is assumed which is consistent with standard 16” o.c. stud framing prac ces. Reduced framing factors may be possible. *EWI = Engineered Wood I-Joist R-values below the R-22 requirement

Plywood and OSB have a dry cup vapour permeance of less than 60 ng/(s•m²•Pa), but are exempted from the requirements for placement of impermeable materials due to having significantly higher wet cup vapour permeance.

Page 28

Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Below Grade Walls Below Grade walls also form an important part of the thermal enclosure of buildings. This sec on provides informa on about two dierent methods for insula ng these walls: Exterior Insulated Interior Insulated

Page 29

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Below Grade Walls

Exterior Insulated Walls This below grade wall assembly consists of rigid insula on placed on the exterior of the concrete founda on wall. A wood stud wall is oMen constructed on the interior of the concrete wall to provide room for electrical and plumbing services. High effec ve R-values of the assembly are achieved by using con nuous insula on outside of the concrete structure. The insula on product used in this arrangement should be highly moisture tolerant and suitable for below grade applica ons. In cold climates, insula on placed on the exterior of the wall increases the temperature of the concrete and consequently oMen reduces the risk of condensa on and associated damage to moisture sensi ve interior wall components and finishes. Drainage is provided at the exterior of the insula on to eliminate hydrosta c pressure on the wall assembly and reduce the risk of water ingress.

Exterior Gravel Fill Exterior Insula on (Extruded Polystyrene) Damp-proofing/ Waterproofing Concrete Founda on Wood Studs Gypsum Wall Board Interior

Key Considera ons: Drainage to deflect water away from the founda on wall and to prevent hydrosta c pressures is important to the long-term performance of this wall assembly with respect to water penetra on.

Detailing of the wall to ensure con nuity of the water resis ve barrier, air barrier, vapour barrier, and insula on at the below grade to above-above grade wall transi on is important to the overall performance.

The exterior of founda on walls can be difficult and expensive to access post-construc on; consequently, it is prudent to design these assemblies conserva vely with respect to water penetra on and to use durable materials.

Page 30

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Below Grade Walls

Exterior Insulated Walls (cont.)

Drainage Adequate control of surface and ground-water is fundamental to the long-term water penetra on resistance of this assembly. An impermeable surface at grade (i.e. clay cap) sloped away from the building in conjunc on with porous media (i.e. gravel fill) and perimeter drainage at the base of the founda on wall (i.e. weeping le) will direct water away from the wall assembly. In situa ons where there is poten al for hydrosta c pressure to be experienced by the assembly, addi onal precau ons must be taken including the use of a fully bonded waterproof membrane instead of a damp-proofing membrane.

Water Resis ve Barrier (Waterproofing/Damp-proofing) Where the wall assembly does not experience hydrosta c pressure, only rela vely minor amounts of water will penetrate past the insula on. In these cases, a dampproofing membrane is sufficient to resist water ingress when used in conjunc on with appropriate joint and crack control details for the concrete wall. However, if hydrosta c pressure is present, a more robust waterproofing membrane should be used as it will be relied upon to prevent water ingress.

Air Barrier The concrete wall is the most air ght element in this assembly and is usually the most straighVorward to make con nuous with adjacent building enclosure assemblies such as the concrete floor slab (or air barrier below the slab) and above grade walls.

Insula on While extruded polystyrene insula on is typically used in this assembly, various types of insula on can be used including high density expanded polystyrene and rigid mineral wool. It is important that the selected insula on product is extremely moisture tolerant as it can poten ally be exposed to significant weZng in this below grade applica on. The exterior insula on in this assembly will maintain the concrete structure at closer to indoor temperatures, consequently typically reducing the risk of condensa on and associated damage.

Vapour Barrier The concrete founda on wall and damp-proofing membrane provide the vapour control in this assembly. Given the below grade nature of this assembly and the generally wet nature of soil, negligible drying of this assembly to the exterior will occur. Consequently, no addi onal vapour barrier should be installed on the interior to facilitate drying of any minor incidental weZng. Other Considera ons A gap or other capillary break should be provided between interior wood framing and the concrete founda on wall. Alterna vely, preserva ve-treated wood can framing can be used. Direct contact of concrete and untreated wood framing members can lead to moisture related damage.

Effec ve Assembly R-value of Exterior Insulated Below Grade Wall Assembly [B²•°F•hr/Btu] R-value/inch of Exterior Insula on Thickness of Exterior Insula on

R-4.0

R-5.0

3 1/2”

16.6

20.1

4”

18.6

22.6

4 1/2”

20.6

25.1

5”

22.6

27.6

5 1/2”

24.6

30.1

6”

26.6

32.6

6 1/2”

28.6

35.1

7”

30.6

37.6

7 1/2”

32.6

40.1

8”

34.6

42.6

R-values below the R-22 requirement This assembly could poten ally also be a split insulated assembly with insula on installed in the stud cavity as well as on the exterior of the concrete. In this arrangement the ra o of interior to exterior insula on should be considered so as to maintain the temperature of the interior concrete surface at rela vely safe levels and avoid condensa on.

For this alterna ve, the building code requires that an interior vapour barrier be installed.

Page 31

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Below Grade Walls

Interior Insulated Walls This below grade wall assembly consists of rigid or spray-in-place air-impermeable moisture tolerant insula on placed on the interior of the concrete founda on wall. Tradi onally many below grade interior insulated walls have been insulated with baD insula on between wood-framing and a polyethylene sheet was used to provide air and vapour control; however, these wall assemblies pose an unacceptable risk, especially for high R-value walls (i.e. R-22 walls). High effec ve R-values of the assembly are instead achieved by using con nuous insula on placed between the concrete founda on wall and an interior stud framed service wall. Placement of insula on on the interior of the concrete founda on wall results in cooler concrete interior surface temperatures and consequently an increased risk of condensa on and associated damaged. A robust interior air barrier should be installed to limit this risk.

Exterior Gravel Fill Damp-proofing/ Waterproofing Concrete Founda on Taped and Sealed Interior Insula on (Extruded Polystyrene) Wood Studs Gypsum Wall Board Interior

Key Considera ons: Drainage to deflect water away from the founda on wall and to prevent hydrosta c pressures is important to the long-term performance of this wall assembly with respect to water penetra on.

Detailing of the wall to ensure con nuity of the water resis ve barrier, air barrier, vapour barrier, and insula on at the below grade to above-above grade wall transi on is important to the overall performance.

The exterior of founda on walls can be difficult and expensive to access post-construc on; consequently, it is prudent to design these assemblies conserva vely with respect to water penetra on and to use durable materials.

Page 32

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Below Grade Walls

Interior Insulated Walls (cont.)

Drainage Adequate control of surface and ground-water is fundamental to the long-term water penetra on resistance of this assembly. An impermeable surface at grade (i.e. clay cap) sloped away from the building in conjunc on with porous media (i.e. gravel fill) and perimeter drainage at the base of the founda on wall (i.e. weeping le) will direct water away from the wall assembly. In situa ons where there is poten al for hydrosta c pressure to be experienced by the assembly, addi onal precau ons must be taken including the use of a fully bonded waterproof membrane instead of a damp-proofing membrane.

Water Resis ve Barrier (Waterproofing/Damp-proofing) Where the wall assembly does not experience hydrosta c pressure, a damp-proofing membrane is sufficient to resist water ingress when used in conjunc on with appropriate joint and crack control details for the concrete wall. However, if hydrosta c pressure is present, then a more robust waterproofing membrane should be used as it will be relied upon to prevent water ingress.

Air Barrier The concrete wall is the most air ght element in this assembly and is usually the most straighVorward element to make con nuous with adjacent assemblies such as the concrete floor slab (or air barrier below the slab) and above grade walls.

However, with interior insula on approaches it is also important that an interior air barrier be maintained to limit the poten al for rela vely warm and moist interior air to flow past the insula on and come in contact with the interior surface of the colder concrete founda on wall. This is oMen achieved through sealing of joints between insula on boards or by use of spray foam products.

Effec ve Assembly R-value of Interior Insulated Below Grade Wall Assembly [B²•°F•hr/Btu] R-value/inch of Interior Insula on

Insula on Extruded polystyrene (XPS) and closed-cell spray polyurethane foam insula on are typically most appropriate for this applica on as they are both insensi ve to poten al moisture within the concrete and are also rela vely air and vapour impermeable. Air permeable insula on products are not generally recommended unless other measures are considered.

Vapour Barrier

Thickness of Interior Insula on

R-5.0

R-6.0

3 1/2”

20.1

23.6

4”

22.6

26.6

4 1/2”

25.1

29.6

The rela vely vapour-impermeable foam insula on (i.e. XPS or closed-cell spray foam) provide the vapour barrier in this assembly. No addi onal vapour barrier should be installed on the interior of the wood stud wall to facilitate drying of any minor incidental weZng.

5”

27.6

32.6

5 1/2”

30.1

35.6

6”

32.6

38.6

Other Considera ons

6 1/2”

35.1

41.6

7”

37.6

44.6

7 1/2”

40.1

47.6

8”

42.6

50.6

Instead of a wood stud wall it is also possible to use only strapping (i.e. furring) fastened through the insula on if a significant gap is not needed for services. An interior finish is required to provide fire protec on for the foam plas c insula on, or alterna vely an intumescent coa ng can be used in some jurisdic ons for an unfinished basement.

R-value below the R-22 requirement

Page 33

Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Alterna ve R-22 Walls This sec on provides a brief overview of alterna ve wall assemblies that could poten ally be used to achieve the R-22 thermal performance target, but are not covered within this guide. These include: Structurally Insulated Panels (SIPs) Interior Insulated Framed Wall Con nuous Strapping Insulated Concrete Forms Insulated Concrete Forms (Below Grade) Interior Rigid Insulated and BaDs (Below Grade)

Page 34

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Alterna ve R-22 Walls - Above Grade

Structurally Insulated Panels This above grade wall assembly consists of manufactured structurally insulated panels (SIPs) consis ng of con nuous rigid insula on (typically EPS) sandwiched between two layers of OSB sheathing. These panels are then assembled to form the exterior enclosure of the building. Typically 5 1/2” of insula on would be required in this assembly to achieve R-22 or greater.

Addressing the joints between panels with respect to construc on tolerances and air barrier con nuity is an important considera on when using this system and manufacturers will typically provided the relevant details.

Joints should be sealed on both the interior and exterior and the gap filled to prevent convec ve looping between panels. A sheathing membrane is typically installed on the exterior of this assembly to provide the water resis ve barrier and the air barrier, or else the SIPs panels can be sealed to provide the air barrier. A stud wall can be constructed on the interior of the SIPs for services.

Structurally Insulated Panels

Interior Insulated Framed Wall

Interior Rigid Insula on

This above grade wall assembly consists of rigid insula on boards (typically extruded polystyrene) installed on the interior of the baD insulated stud wall. This assembly is similar in principle to the exterior insula on strategy for increasing the wall R-value, though successful applica on is oMen more difficult. In cold climates, the addi onal depth of insula on installed on the interior side of the exterior sheathing can slightly decrease the sheathing temperature and consequently increase the risk of condensa on on the moisture-sensi ve wood sheathing and framing. The rigid insula on should be sealed to provide the air barrier, and low permeability of the insula on boards is also adequate to provide the vapour barrier. Installa on and sealing of electrical outlets and other service penetra on can be difficult when using this wall assembly. Interior gypsum wall board can be installed on ver cal strapping to provide an interior finish as well as fire protec on.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Alterna ve R-22 Walls - Above Grade

Con nuous Strapping This above grade wall assembly consists of rigid or semirigid insula on placed on the exterior of a conven onal above grade, insulated 2x4 or 2x6, wood-frame wall assembly; however, in this case the cladding support is provided using ver cal strapping which con nuously penetrates through the exterior insula on. While rela vely uncommon, this method can provide addi onal cladding support as compared to only fasteners through the insula on. The con nuous wood members which penetrate the exterior insula on must be considered in the calcula on of the wall effec ve R-value in a manner similar to that used for stud walls (i.e. parallel paths). Due to the reduc on of the insula on performance by the con nuous strapping, addi onal insula on thickness is required for this assembly to achieve the same thermal performance as an exterior insulated assembly with only fasteners or thermally efficient clips through the insula on. Other considera ons for this assembly are similar to those for the exterior insulated above grade assembly.

Con nuous Strapping

Insulated Concrete Forms (Above Grade)

Insulated Concrete Forms

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This wall assembly consists of Insulated Concrete Forms (ICFs) which are manufactured interlocking modular concrete formwork made of rigid expanded polystyrene (EPS) insula on. Once assembled, these forms are filled with concrete and remain in place to provide insula on.

While typically this type of construc on is used for below grade walls, it can also be applied to above grade walls.

High effec ve R-values of the assembly are achieved by the combina on of the interior and exterior form layers, and to meet R-22 typically at least 5” of total insula on thickness will be required. OMen a stud wall is built to the interior of this assembly to provide a space for services and facilitate aDachment of gypsum wall board for an aesthe c finish as well as fire protec on of the foam plas c insula on. Some ICFs provide channels for services which can be used instead of construc ng an interior stud wall.

Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Alterna ve R-22 Walls - Below Grade

Insulated Concrete Forms (Below Grade) This wall assembly consists of Insulated Concrete Forms (ICFs) which are manufactured interlocking modular concrete forms made of rigid expanded polystyrene (EPS) insula on. Once assembled, these forms are filled with concrete and remain in place to provide insula on. While typically this type of construc on can be used in above grade applica ons, it is more commonly use for below grade walls. High effec ve R-values of the assembly are achieved by the combina on of the interior and exterior form layers, and a typical ICF will meet R-22 with a total insula on thickness of approximately 5”. In below grade applica ons a damp-proofing or waterproofing material should be applied to the exterior insula on. A stud wall is some mes built to the interior of this assembly to provide a space for services and facilitate aDachment of gypsum wall board. Some ICFs provide channels for services in the foam insula on which can be used instead of construc ng an interior stud wall, and embedded fastening points for interior drywall.

Insulated Concrete Forms

Interior Rigid Insula on and BaPs

Interior BaP and Rigid Insula on

This below grade wall is similar to the interior insulated below grade wall assembly that is insulated with rigid or spray-in-place, air-impermeable, moisture tolerant, insula on placed on the interior of the concrete founda on wall. The primary difference is that that this wall also includes baD insula on in the stud cavity. Using baD insula on in the stud cavity can provide the required Rvalue while allowing for a reduc on in the amount of rigid insula on which is required. The rigid insula on is used as the air barrier in this assembly, and an interior vapour barrier (interior of the baD insula on) is s ll required to meet code requirements. Given the limited outward drying capacity of this assembly, it may be prudent to use a rela vely permeable interior vapour barrier such as a smart vapour retarder or vapour barrier paint. A minimum of 2” of rigid foam or spray foam insula on is required between the stud and concrete walls to achieve R-22 and limit the poten al for condensa on within the wall assembly.

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Walls Less Than R-22 This sec on provides a brief overview of wall assemblies that would not be adequate to achieve the R-22 thermal performance target.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Walls Less Than R-22 While the majority of this guide is dedicated to iden fying walls which achieve the R-22 or greater thermal performance requirement of the 2014 VBBL (and the BCBC 2012 for climate zones 7B and 8), this sec on iden fies assemblies which specifically do not meet this requirement, when constructed using standard framing prac ces. (i.e. 23% framing factor for 16” o.c. studs)

2x6 Stud Walls with Insula on Only in the Stud Cavity (regardless of the insula on type)

2x4 Double Stud Wall on 2x6 with Staggered Overlapping Studs (It is also nearly impossible to reach R-22 without a gap between the two stud walls)

Exterior Insulated Stud Wall with 3” or less of Insula on (regardless of the insula on type)

Exterior Insulated Wall with Con nuous Strapping and 4” or less of Insula on (regardless of the insula on type)

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Illustrated Guide to R22+ Eec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Summary This sec on provides a summary of the wall assemblies covered in this guide including minimum insula on levels to achieve R-22 and also provides a list of other available resources to assist in the design of enclosure assemblies and systems.

Summary of Walls Addi onal Resources

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Summary of Walls Detailed discussions of each assembly including thermal performance values have been provided throughout the guide. This sec on provides a summary of the minimum insula on levels required for each assembly to achieve R-22 effec ve as well as key considera ons for ease of reference. It should be noted that the R-values of these assemblies will vary slightly depending on specific assembly layer selec ons (i.e. cladding), but that generally the values provided are intended to be slightly conserva ve.

Interior Insulated

Exterior Insulated

Deep Stud

Double Stud

Exterior Insulated

Split Insulated

Minimum Insula on Levels to Achieve R-22 Effec ve

Key Considera ons

The vapour permeability of the sheathing 2x4 Studs (R-12 BaDs) + 3” R-4/inch or 2 1/2” R-5/inch Ext. Ins. membrane and the exterior insula on should be 2x6 Studs (R-19 BaDs) + 1 1/2” of R-4/inch or R-5/inch Ext. Ins. carefully considered so as not to create a risk of 2x6 Studs (R-22 BaDs) + 1” of R-5/inch Ext. Ins. condensa on within the assembly, or to intolerably 2x6 Studs (R-24 BaDs) + 1” of R-4/inch Ext. Ins. reduce the ability of the assembly to dry.

2x4 or 2x6 Studs (No BaDs) + 5” R-4/inch or 4” R-5/inch

The method of cladding aDachment is important to limit thermal bridging through the exterior insula on while adequately suppor ng the exterior cladding.

Con nuity of the air barrier and installa on of a vapour barrier are fundamental to the 2x4 Double Stud Wall with No Gap and R-5/inch Insula on performance of this assembly as the slightly 2x4 Double Stud Wall with 1/2” Gap and R-4/inch Insula on 2x4 Double Stud Wall with 1” Gap and R-3.4/inch Insula on decreased exterior sheathing temperature increases the risk of condensa on and related damage.

2x8 Stud Wall with R-4 or R-5/inch Insula on 2x10 Stud Wall with R-3.4/inch Insula on 8” Engineered Wood I-Joist with R-3.4/inch or R-4/inch or R-5/inch insula on

Con nuity of the air barrier and installa on of a vapour barrier are fundamental to the performance of this assembly as the slightly decreased exterior sheathing temperature increases the risk of condensa on and related damage.

5” R-4/inch Insula on or 4” R-5/inch Exterior Insula on

The exterior of founda on walls can be difficult and expensive to access post-construc on; consequently, it is prudent to design these assemblies conserva vely with respect to water penetra on and to use durable materials.

4” R-5/inch Insula on or 3 1/2” R-6/inch Interior Insula on 2 1/2” R-5/inch + 2x4 Studs (R-12 BaDs)

Detailing of the wall to ensure con nuity of the water resis ve barrier, air barrier, vapour barrier, and insula on at the below grade to above-above grade wall transi on is important to the overall performance.

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Addi onal Resources This guide provides an overview of different assemblies which can poten ally be used to meet an R-22 performance requirement.

Other resources are also available which provide more detailed informa on regarding building enclosure systems and design.

Design Guides Illustrated Guide—Energy Efficiency Requirements for Houses in Bri sh Columbia published by BC Housing.

(Available at www.hpo.bc.ca) Guide for Designing Energy-Efficient Building Enclosures for Wood-Frame Mul -Unit Residen al Buildings published by FP Innova ons, BC Housing, and the Canadian Wood Council.

(Available at fpinnova ons.ca) Building Envelope Guide for Houses published by BC Housing.

(Available at www.hpo.bc.ca) Building Enclosure Design Guide published by BC Housing.

(Available at www.hpo.bc.ca) Canadian Home Builder’s Associa on Builders’ Manual published by the Canadian Home Builders’ Associa on.

(Available at www.chba.ca/buildermanual.aspx) Canadian Wood-Frame House Construc on published by the Canada Mortgage and Housing Corpora on (CMHC).

(Available at www.cmhc-schl.gc.ca) Residen al Construc on Performance Guide published by BC Housing (Available at www.hpo.bc.ca) Builder’s Guide to Cold Climates published by Building Science Corpora on.

(Available at www.buildingsciencepress.com) Pathways to High-Performance Housing in Bri sh Columbia published by FPInnova ons.

(Available at fpinnova ons.ca) Structural Design Guides and References Guide to A1aching Sheathing, Furring and/or Cladding through Con nuous Foam Insula on to Wood Framing, Steel Framing, Concrete and CMU Substrates with TRUFAST SIP TP, SIP LD and Tru-Grip Fasteners published by NTA Inc. (Available at www.trufast.com) External Insula on of Masonry Walls and Wood Framed Walls published by The Na onal Renewable Energy Laboratory (U.S. Department of Energy) (Available at www.n s.gov) Roxul - ComfortBoard (IS) Deflec on Tes ng published by Building Science Corpora on.

(Available at www.roxul.com) Guide to A1aching Exterior Wall Coverings through Foam Sheathing to Wood or Steel Wall Framing published by Foam Sheathing Coali on (Available at www.hunterpanels.com)

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Illustrated Guide to R22+ Effec ve Walls in Wood-Frame Construc on in Bri sh Columbia

Addi onal Resources (cont.)

Technical Informa on Study of Moisture-Related Durability of Walls with Exterior Insula on in the Pacific Northwest by Building Science Corpora on.

(Available at www.buildingsciencelabs.com) Wall Thermal Design Calculator by the Canadian Wood Council (Available at www.cwc.ca) Building Envelope Thermal Bridging Guide published by BC Hydro and BC Housing.

(Available at www.bchydro.com) ASHRAE Handbook of Fundamentals 2013 published by the American Society of Hea ng, Refrigera ng, and Air-Condi oning Engineers (ASHRAE).

(Available at www.ashrae.org) Building Codes Vancouver Building By-law (VBBL) 2014 published by the Queen’s Printer for Bri sh Columbia (Available at hDp://vancouver.ca/your-government/vancouver-building-bylaw.aspx) Bri sh Columbia Building Code (BCBC) 2012 published by the Queen’s Printer for Bri sh Columbia (Available at hDp://www.bccodes.ca/building-code.aspx?vid=QPLEGALEZE:bccodes_2012_view)

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